Apparatus for forming fins



Jan. 29, 1957 sc us R 2,779,223

APPARATUS FOR FORMING FINS Filed Aug. 24, 1955 aa iL ['7' f J4 //W f Z l /8 F 1 -E 32f flew/770x? A. 60/7 uJfe/ INVENTOR.

Un ted States Paten APPARATUS FOR FORMING FINS Herman A. Schustcr, Houston, Tex.

Application August 24, 1955, Serial No. 530,248 3 Claims. (c1. so--1s This invention relates to an apparatus for forming fins and more particularly to an apparatus for forming extruded helical this on a length of stock.

Thisinvention relates to an apparatus of the general type disclosed in Patent No. 2,508,518, granted May 23, 1950 on the application of Walter P. Hill for an apparatus for forming integral fins on a length of stock.

It is common practice in the art of forming integral helical fins from a length of stock to be used as heat exchangers for a tubular blank of comparatively soft metal to be engaged by a plurality of forming rollers mounted for rotation with their respective axes extending in the general direction of the axis of the tu'bular'blank and spaced around the blank. The axes of the rollers are arranged at such an angle to the axis of the tubular blank as to enable the rollers to travel a helical path around the blank corresponding to the helix angle of the fin formed on the rollers by the action of annular discs forming a part of the rollers. This fin is fashioned to the desired cross sectional contour by the upper and lower surfaces or the discs of the rollers between which discs the comparatively soft metal of the blank is extruded. The periphery of each disc on the roller and that part of the surface of each disc contacting the extruded metal from the blank have been subject to varied design to attempt to overcome numerous problems in forming of the helical fin. One problem sought to be overcome is the forming of a perfect helix in which the threads of the fin are not warped by the fin forming apparatus or otherwise bent as it is highly desirable to have the threads always equally spaced from one another to increase the heat transferring qualities of the product, its appearance and its sales appeal.

It is therefore a general object of the present invention to provide an apparatus for forming a helical fin from a length of stock in which apparatus the annular discs do not cause warping or other disfiguration of the threads of the fin.

One essential in forming such a perfect helix with unwarped threads is that the various discs on the rollers trac each other as accurately as possible. It is therefore another object of the present invention to provide a fin forming apparatus in which the annular rings on the rollers accurately track one another.

It is a more specific object of the present invention to provide a fin forming apparatus in which the trailing sides oi the annular discs on the rollers are at a constant angle with a plane perpendicular to the axis of rotation of the discs and which angle is between about 0.5 and about 1.0 degree.

Still another object of the present invention is to provide such an improved fin forming apparatus which is simple and economical to construct and which is efficiently reliable in operation.

Other objects, features and advantages will be more apparent from the following description of a preferred example of the invention, given for the purpose of disclosure, and taken in conjunction with the accompanying Patented Jan. 29, 1957 "ice 2 drawing where like character references refer to like parts throughout the several views and where Figure 1 is a cross sectional view of the apparatus according to the present invention shown engaging a tubular blank, I

Figure 2 is an enlarged cross sectional view of oneot' the annular discs of the present invention, and

Figure 3 is a sectional elevation taken along the line 3--3 of Figure 1.

Referring now to the drawings, and particularly to Figures 1 and 3, a helical fin 10 is formed from a normally tubular blank or length or" stock 12 of extrudable material, which stock is supported during the fin forming operation by a mandrel 14 passing axially through the length of stock or the blank 12. A plurality of rollers indicated generally by the reference numeral 16, usually three in number, are distributed about the circumference of the stock 12, as best illustrated in Figure 1, and when three are used they are normally spaced degrees apart. Each roller includes an arbor 18 which carries thereon a plurality of annular fin forming discs 20, each such disc 20 being mounted proximate an adjacent disc and each Such disc having its axis of rotation the same as that of the axis of the arbor.

The discs 29 are secured to the arbor 18 to move therewith, such as by the pin 22 passing through each disc 20 and being secured in the hubs 24 at each end of arbor 18 although they may be secured in other ways.

in operation, the axes of the arbors 18 are slightly crossed with respect to the axis of the stock 12 and also arranged at such an angle to the axis of the stock 12 so that the discs 20 will travel a helical path about the stock 12. With this construction the discs 20 tend to track one another and cooperate to form a continuous helical fin on the surface of the stock 12, as will hereafter be more fully described. The arbors 13 are driven by any suitable driving means (not shown) and are supported in any conventional manner to enable the rollers 16 to be moved toward or away from stock 12.

This construction heretofore described is well known in the art and no further description thereof is deemed necessary.

In 0 oration, after a length of stock 12 is properly supported by mandrel 14, the rollers 16 are swung inwardly until the discs 20 contact the periphery of the stock 12 in the position shown in Figure 1. Because of the angular relationship between the axes of the discs 20 and the stock 12, rotation of the discs 20 by means of the arbor 18 causes the stock 12 to rotate and axially advance resulting in the discs 20 traversing a helical path with respect to the axes of the blank 12. As this occurs the generally radially inwardly directed pressure on the blank 12 by the discs 20 depresses the extrudable metal of the blank 12 to displace this material outwardly into the grooves 26 between the discs 20 adjacent their peripheries 28.

v The leading or front edge 30 of the periphery 28 of each disc 20 is normally cut at an even or successively decreasing angle, as best seen in Figure 3, although other shapes of the leading edge 30 may be utilized.

The present invention is based upon the surprising discovery and unexpected benefits resulting from maintain ing the angle of the trailing or back surfaces of the discs 20 constant. As best seen in Figure 2, there is formed on the trailing or back side 32 of each disc 20 a flat annular trailing surface 34 which forms an angle 38 with a plane perpendicular to the axes of rotation of discs 20 and which fiat trailing surface is inclined from the apex of this angle toward the leading side 36 of the disc. This angle, indicated by the numeral 38 in Figure 2, is constant on all discs on all of the rollers 16 used for forming fins on any one particular blank 12. This angle 38 is critical and ranges from between about 0.5 and about 1.0 degree. The runout starts at the same point or radius on all the discs. In other words the trailing or back sides of the discs are parallel to one another.

It has been found that there are surprisingly improved results in the tracking ability of the discs 20, the uniformity of spacing between the threads of the fin 10, and a lack of warping and other deformation of fin 10 if this angle 30 is kept constant on all fins 20 on all the rollers and if it is not less than about 0.5 degree or more than about 1.0 degree. With variations in this angle 38 between various discs 20 or if the angle is beyond these critical measurements then the ability of the apparatus to form evenly spaced threads in the fin 20 and to eliminate warping and other deformation is sharply decreased.

As long as the trailing angle 38 is maintained as specified above, the discs 20 may vary considerably such as having different diameters and having different shaped leading edges 30.

The present invention, therefore, is well suited to carry out the objects and attain the advantages mentioned, as well as others inherent therein.

While only a single example of the apparatus has been given for the purpose of illustration, changes in details and rearrangement of parts will readily suggest themselves to those skilled in the art, and accordingly the invention is limited only by its spirit as defined by the scope of the appended claims.

What is claimed is:

1. An improved roller for forming a helical fin from a length of stock of circular cross section comprising, an arbor, a plurality of annular fin forming discs mounted proximate each other on said arbor with an axis for rotation of each disc the same as that of the arbor, each said disc having leading and trailing sides, and an annular fiat trailing surface on the trailing side of each disc at the periphery of each disc directed outwardly toward the leading side of said disc, each said trailing surface forming an angle with a plane perpenicular to the axes of rotation of the discs and starting at the same radial point, said angle being from about 0.5 to about 1.0 degree and being the same on. each disc.

2. in a roller for forming a helical fin from a length of stock of circular cross section, said rollers having an arbor, a plurality of annular fin forming discs mounted proximate each other on said arbor with an axis for r0- tation of each disc the same as that of the arbor, each said disc having leading and trailing sides, the improvement comprisingan annular flat trailing surface on the trailing side of each disc at the periphery of each disc directed outwardly toward the leading side, said trailing surface forming an angle with a plane perpenicular to the axes of rotation of the. discs and starting at the same radial point, said angle being from about 0.5 to about 1.0 degree and being the same on each disc.

3. An apparatus for forming a helical fin from a length of stock of circular cross section comprising, a plurality of rollers distributed about the circumference of the stock with their axes extending generally in the direction of the length of the stock, each said roller comprising an arbor, a plurality of annular fin forming discs mounted proximate each other on said arbor and perpendicular thereto, each said disc having leading and trailing sides, an annular fiat trailing surface on the trailing side of each disc at the periphery of each disc directed outwardly toward the leading side, said trailing surface forming an angle with a plane perpendicular to the axis of rotation of the disc and starting at the same radial point, said angle being from about 0.5 to about 1.0 degree and being the same on each disc.

References Cited in the file of this patent UNITED STATES PATENTS 

